Fury was ringside in Saudi Arabia to watch Joshua brutally knock out MMA superstar Francis Ngannou in two rounds.
It was in the same arena just five months earlier that he was floored by Ngannou and deemed fortunate to escape with a split-decision win.
So Hearn stated AJ’s stunning stoppage punched him to the top of the heavyweight division.
But Fury – who faces the man who twice beat Joshua in Oleksandr Usyk – was quick to shut down the promoter.
He said on BBC: “Congratulations to Joshua, but listen we all know styles make fights and Eddie Hearn’s shouting he’s the best heavyweight in the world, we know he’s not.
“He’s already been beaten by Usyk twice and I’ve got to deal with that problem for him.
“So after I’ve done that – twice – and if he’s still available, we’ll get it on. Get it on like Donkey Kong!”
Fury was due to unify all four belts – for the first time in heavyweight history – on February 17 until he suffered a cut in sparring two weeks out.
The freak injury has instead backdated the historic title bout to May 18 and the WBC champion insisted the gash is healed up.
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Fury said: “Can’t see it because it’s gone, the cut’s gone. So it is what it is. I’m ready to roll and roll. I’ll see you on May 18th.”
Joshua’s promoter Hearn has thrown his support Fury’s way so that the Battle of Britain can finally commence.
He said: “You are looking at the baddest man on the planet. The No 1 heavyweight in the world.
“There’s a brilliant fighter down there in Tyson Fury. Please beat Oleksandr Usyk, because you will get the biggest fight of all time.”